High strength and multifunctional polyurethane film incorporated with lignin nanoparticles

Abstract

Polyurethane (PU) has a wide application in the chemical, electronic and textile industries due to its high ductility, toughness, and good thermal stability. However, the generation of strong and multifunctional PU film is challenging. Herein, lignin nanoparticle (LNP), which was produced from black liquor (i.e., a waste stream from the wheat straw pulping process) using biomass based γ- valerolactone via nanoprecipitation, was used as a nano-filler for enhancing the strength of the PU film. The well distributed LNP had nano-sized particles and abundant phenolic hydroxyl groups, which could act as lubricating agents when incorporated into the PU matrix, thus leading to energy dissipation. By developing additional hydrogen bonds, LNP enhanced the tensile strength and elongation of the PU film. The maximum tensile strength and elongation at break of 50.7 MPa and 755.8% were achieved, while pure PU film had 18.4 MPa and 223.2% tensile strength and elongation, respectively. In addition, the natural inherent properties of lignin endowed the PU film with multifunctional properties, such as hydrophobicity, anti-ultraviolet, and better hydrothermal stability. Based on these interesting results, the LNP incorporation into the PU film could further broaden the practical utilization of the PU film.